The Speech at the Forum of Art and Literature in Yan’an is the representative work of Mao Zedong’s thought about the unity of the Party spirit and popularity of literature and art. This thought has both theoretical and realistic foundations. The Party spirit of literature and art includes the definitions both on the natural and the realistic levels. Adhering to the Party spirit of literature and art demands that the Party member writers must join the Party in thinking, that all the writers must study Marxism seriously, and that literature and art must be subject to politics rather than to individual politicians. Popularity is embodied in the object, the content and the evaluation standard of the literature and art. Mao Zedong’s discussions about relations between popularization and improvement, teaching and learning, motivation and effect show the demand of popularity of literature and art. It is of realistic significances to adhere to the unity of the Party spirit and the popularity of literature and art today.